/**
 * Copyright (c) E.Y. Baskoro, Research In Motion Limited.
 * 
 * Permission is hereby granted, free of charge, to any person
 * obtaining a copy of this software and associated documentation
 * files (the "Software"), to deal in the Software without 
 * restriction, including without limitation the rights to use, 
 * copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the 
 * Software is furnished to do so, subject to the following 
 * conditions:
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES 
 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT 
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, 
 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING 
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR 
 * OTHER DEALINGS IN THE SOFTWARE.
 * 
 * This License shall be included in all copies or substantial 
 * portions of the Software.
 * 
 * The name(s) of the above copyright holders shall not be used 
 * in advertising or otherwise to promote the sale, use or other 
 * dealings in this Software without prior written authorization.
 * 
 */
package com.walkline.util.json;

import java.io.IOException;
import java.io.Writer;

/**
 * JSONWriter provides a quick and convenient way of producing JSON text. The texts produced strictly conform to JSON syntax rules. No whitespace is added, so the results are ready for transmission or storage. Each instance of JSONWriter can produce one JSON text.
 * <p>
 * A JSONWriter instance provides a <code>value</code> method for appending values to the text, and a <code>key</code> method for adding keys before values in objects. There are <code>array</code> and <code>endArray</code> methods that make and bound array values, and <code>object</code> and <code>endObject</code> methods which make and bound object values. All of these methods return the JSONWriter instance, permitting a cascade style. For example,
 * 
 * <pre>
 * new JSONWriter(myWriter).object().key(&quot;JSON&quot;).value(&quot;Hello, World!&quot;).endObject();
 * </pre>
 * 
 * which writes
 * 
 * <pre>
 * {"JSON":"Hello, World!"}
 * </pre>
 * <p>
 * The first method called must be <code>array</code> or <code>object</code>. There are no methods for adding commas or colons. JSONWriter adds them for you. Objects and arrays can be nested up to 20 levels deep.
 * <p>
 * This can sometimes be easier than using a JSONObject to build a string.
 * 
 * @author JSON.org
 * @version 2
 */
public class JSONWriter {
	private static final int maxdepth = 20;

	/**
	 * The comma flag determines if a comma should be output before the next value.
	 */
	private boolean comma;

	/**
	 * The current mode. Values: 'a' (array), 'd' (done), 'i' (initial), 'k' (key), 'o' (object).
	 */
	protected char mode;

	/**
	 * The object/array stack.
	 */
	private char stack[];

	/**
	 * The stack top index. A value of 0 indicates that the stack is empty.
	 */
	private int top;

	/**
	 * The writer that will receive the output.
	 */
	protected Writer writer;

	/**
	 * Make a fresh JSONWriter. It can be used to build one JSON text.
	 */
	public JSONWriter(Writer w) {
		comma = false;
		mode = 'i';
		stack = new char[maxdepth];
		top = 0;
		writer = w;
	}

	/**
	 * Append a value.
	 * 
	 * @param s
	 *            A string value.
	 * @return this
	 * @throws JSONException
	 *             If the value is out of sequence.
	 */
	private JSONWriter append(String s) throws JSONException {
		if (s == null) {
			throw new JSONException("Null pointer");
		}
		if ((mode == 'o') || (mode == 'a')) {
			try {
				if (comma && (mode == 'a')) {
					writer.write(',');
				}
				writer.write(s);
			} catch (IOException e) {
				throw new JSONException(e);
			}
			if (mode == 'o') {
				mode = 'k';
			}
			comma = true;
			return this;
		}
		throw new JSONException("Value out of sequence.");
	}

	/**
	 * Begin appending a new array. All values until the balancing <code>endArray</code> will be appended to this array. The <code>endArray</code> method must be called to mark the array's end.
	 * 
	 * @return this
	 * @throws JSONException
	 *             If the nesting is too deep, or if the object is started in the wrong place (for example as a key or after the end of the outermost array or object).
	 */
	public JSONWriter array() throws JSONException {
		if ((mode == 'i') || (mode == 'o') || (mode == 'a')) {
			push('a');
			append("[");
			comma = false;
			return this;
		}
		throw new JSONException("Misplaced array.");
	}

	/**
	 * End something.
	 * 
	 * @param m
	 *            Mode
	 * @param c
	 *            Closing character
	 * @return this
	 * @throws JSONException
	 *             If unbalanced.
	 */
	private JSONWriter end(char m, char c) throws JSONException {
		if (mode != m) {
			throw new JSONException(m == 'o' ? "Misplaced endObject." : "Misplaced endArray.");
		}
		pop(m);
		try {
			writer.write(c);
		} catch (IOException e) {
			throw new JSONException(e);
		}
		comma = true;
		return this;
	}

	/**
	 * End an array. This method most be called to balance calls to <code>array</code>.
	 * 
	 * @return this
	 * @throws JSONException
	 *             If incorrectly nested.
	 */
	public JSONWriter endArray() throws JSONException {
		return end('a', ']');
	}

	/**
	 * End an object. This method most be called to balance calls to <code>object</code>.
	 * 
	 * @return this
	 * @throws JSONException
	 *             If incorrectly nested.
	 */
	public JSONWriter endObject() throws JSONException {
		return end('k', '}');
	}

	/**
	 * Append a key. The key will be associated with the next value. In an object, every value must be preceded by a key.
	 * 
	 * @param s
	 *            A key string.
	 * @return this
	 * @throws JSONException
	 *             If the key is out of place. For example, keys do not belong in arrays or if the key is null.
	 */
	public JSONWriter key(String s) throws JSONException {
		if (s == null) {
			throw new JSONException("Null key.");
		}
		if (mode == 'k') {
			try {
				if (comma) {
					writer.write(',');
				}
				writer.write(JSONObject.quote(s));
				writer.write(':');
				comma = false;
				mode = 'o';
				return this;
			} catch (IOException e) {
				throw new JSONException(e);
			}
		}
		throw new JSONException("Misplaced key.");
	}

	/**
	 * Begin appending a new object. All keys and values until the balancing <code>endObject</code> will be appended to this object. The <code>endObject</code> method must be called to mark the object's end.
	 * 
	 * @return this
	 * @throws JSONException
	 *             If the nesting is too deep, or if the object is started in the wrong place (for example as a key or after the end of the outermost array or object).
	 */
	public JSONWriter object() throws JSONException {
		if (mode == 'i') {
			mode = 'o';
		}
		if ((mode == 'o') || (mode == 'a')) {
			append("{");
			push('k');
			comma = false;
			return this;
		}
		throw new JSONException("Misplaced object.");

	}

	/**
	 * Pop an array or object scope.
	 * 
	 * @param c
	 *            The scope to close.
	 * @throws JSONException
	 *             If nesting is wrong.
	 */
	private void pop(char c) throws JSONException {
		if ((top <= 0) || (stack[top - 1] != c)) {
			throw new JSONException("Nesting error.");
		}
		top -= 1;
		mode = top == 0 ? 'd' : stack[top - 1];
	}

	/**
	 * Push an array or object scope.
	 * 
	 * @param c
	 *            The scope to open.
	 * @throws JSONException
	 *             If nesting is too deep.
	 */
	private void push(char c) throws JSONException {
		if (top >= maxdepth) {
			throw new JSONException("Nesting too deep.");
		}
		stack[top] = c;
		mode = c;
		top += 1;
	}

	/**
	 * Append either the value <code>true</code> or the value <code>false</code>.
	 * 
	 * @param b
	 *            A boolean.
	 * @return this
	 * @throws JSONException
	 */
	public JSONWriter value(boolean b) throws JSONException {
		return append(b ? "true" : "false");
	}

	/**
	 * Append a double value.
	 * 
	 * @param d
	 *            A double.
	 * @return this
	 * @throws JSONException
	 *             If the number is not finite.
	 */
	public JSONWriter value(double d) throws JSONException {
		return this.value(new Double(d));
	}

	/**
	 * Append a long value.
	 * 
	 * @param l
	 *            A long.
	 * @return this
	 * @throws JSONException
	 */
	public JSONWriter value(long l) throws JSONException {
		return append(Long.toString(l));
	}

	/**
	 * Append an object value.
	 * 
	 * @param o
	 *            The object to append. It can be null, or a Boolean, Number, String, JSONObject, or JSONArray, or an object with a toJSONString() method.
	 * @return this
	 * @throws JSONException
	 *             If the value is out of sequence.
	 */
	public JSONWriter value(Object o) throws JSONException {
		return append(JSONObject.valueToString(o));
	}
}
